Need help with a slightly advanced A/B+looper switch

[ledet]

Hi, just joined this cool forum looking for some help with a project I'm doing for a friend.

He plays guitar and keys in our band, and he requires some clever, but simple switching.
What he needs is a pedal with two switches that does the following:

Switch A:
Pos 1: Guitar goes through pedalboard (in one big true bypass loop) and out through his guitar amp (Amp 1). Keys go straight to the PA.
Pos 2: Guitar is muted. Keys go through the pedalboard loop and on to the next switch...

Switch B:
Pos 1: Keys (with pedals) go through the PA.
Pos 2: Keys (with pedals) go through a dedicated amp (Amp 2).

I have tried making a diagram with a 4PDT switch for switch A and a 3PDT switch for switch B, but I'm not sure if it's gonna work.
My main concern is that the PA needs to be able to receive signal from both switch A and B, depending on the setting.

E.g.: Both switches are in pos 2. That means the PA isn't getting any signal, which means that it should go to ground in both switches to be muted. But, if I switch B to pos 1, the PA with both be connected to the hot signal from the keys (with pedals) AND the ground from switch A.

At least that seems to be the case with my current diagram. Do you understand the problem? Is it a problem at all? Will the PA receive the sound even though it's going to ground and hot at the same time?

Do you have any other ideas for how I should wire this thing up based on the requirements?

For your info, the components will be(for now):

7 jacks (guit input, keys input, fx send, fx return, amp 1 out, amp 2 out, pa out)
1 4PDT switch
1 3PDT switch
1 9VDC
4 LEDS

Thanks in advance, I hope someone has a better mind for this than I do! 

[jpwilksch]

Hi ledet, welcome to the forum :-)

Can you share your current diagram with us?

[ledet]

Sure, here it is, though it's not exactly pretty (or very readable):



Let me know if you have doubts about how to read it, or tell me if I have to make a more clear one.

[PRR]

> tell me if I have to make a more clear one.

If you can't draw it clearly, you can't build it.

If we can't read the drawing on-sight, then it isn't clear enough. (Mostly because if we have to wrap and rack our brains, it's easier to move on to another thread.)

Thoughts:

You have drawn final-layout. It *may* be better to work as pure concept, without regard for how it will finally be laid-out. Here's my first-sketch, most switching To Be Determined...



I see LEDs but no series resistors?

[ledet]

When I drew it I just thought I'd be able to work it out for myself, so I just made a quick diagram like I usually do with projects like these.
I've drawn the actual concept over and over to find the most efficient way of doing the required switching - it's the actual wiring of the thing I'm having trouble with.
To be specific it's just the PA connected to both switches that makes me wonder if it'll work.

Anyway, I tried to make a more clear diagram - there are still a lot of messy wires, but this time they're color coded so it should be easier to read.

[duck_arse]

like paul says, wrapping and wracking. I always have trouble looking at the mechanical drawings of switching problems, much less problems when it is an electrical drawing. the one with the dots and arrows for switch poles and throws, like prr's "PA kamp" scrawl.

[ledet]

I guess the main thing I'm trying to get an answer to here is: Can I have the PA jack connected to both switches, meaning that in a specific setting, the PA will connect to both hot signal and ground? Will that get me the desired sound, will it get me noise, or will it just give me no sound at all?

[samhay]

Do you really need to ground input / outputs in bypass?

[ledet]

Well, that's part of the question - if I don't have to connect the PA to ground when it's off, and I won't get any noise if it just isn't connected to anything, then that would be the easiest fix.

[caspercody]

You might find some information on this website:

http://www.singlecoil.com/tb-strip/tbstrip.html

Rob

[slacker]

How you've drawn it now, if you select Amp 2 with the 3PDT then the input of the PA is grounded, so if you have the 4PDT in position 1 you'll get no sound from the keyboard, because the input to the PA is grounded. It's unlikely but this could damage the keyboard because you're also connecting it's output to ground.
You could try it without grounding the PA input it might work fine but it could be noisy. You are also leaving amp 1 input connected to nothing in position 2 of the 4PDT, so you could have noise problems there as well.

[slacker]

You could replace switch A with this, also a 4PDT



The block in the middle is the pedal board
From guitar/pedals is from the guitar
To pedals/amp input goes to amp 1

Amp effects send is from the keyboard
Amp effects return is to switch B which is wired the same as you have it now

In one position the guitar goes through the pedal board to amp 1 and the keyboard goes straight to switch 2
In the other position the guitar goes straight to amp 1 and the keyboard goes through the pedal board and then to switch 2

This doesn't do exactly what you want but it achieves the same thing, with the addition that you can have the keyboard straight through amp 2 if you want. There's no issues with having to ground the guitar amp because the guitar is always attached, just turn down the guitar's volume to silence it.
You loose out on the LEDs for switch A but if your friend can't remember what he's supposed to be playing at a given point his rig is probably too complicated for him You could use a rotary switch for switch A that does away with the need for LEDs, I don't think something like this needs to be stompable.